If Amazon Best Sellers are a good judge of what are the best books to buy for learning the C computer programming language I would say to check these out: C Programming Language, 2nd Edition, C Programming Absolute Beginner's Guide (3rd Edition), Programming in C (4th Edition) (Developer's Library), C Programming: A Modern Approach, 2nd Edition, C Programming in One Hour a Day, Sams Teach Yourself (7th Edition), Problem Solving and Program Design in C, Fourth Edition, A Book on C: Programming in C (4th Edition), and C in a Nutshell: The Definitive Reference 2nd Edition.
